Tillage implements having safety trip mechanisms for protecting an earthworking tool against damage when an obstruction is encountered have been well known in the past. These units can normally be placed in two general categories. The first category consists of safety trip mechanisms which will automatically reset the earthworking tool with respect to the frame after the earthworking tool has cleared the obstruction. The other type of safety trip mechanism may be referred to as a manual reset type of unit which is operated when an obstruction is encountered and the operator must then perform some operation to return the ground or earthworking tool to its operative position.
Both of these types of units again may be categorized into two general categories. The first of these categories may be referred to as a pneumatic safety trip mechanism while the second category consists of spring biased safety trip mechanisms.
Examples of spring type trip mechanisms are shown in U.S. Pat. No. 3,662,839, issued May 16, 1972; U.S. Pat. No. 2,860,564, issued Nov. 18, 1958; and U.S. Pat. No. 2,756,659, issued July 31, 1956.
The known type of spring biased trip mechanisms require either an extremely large spring that produces a force greater than the forces acting on the tool or an extremely complicated camming mechanism or both. Both types of spring trip mechanisms, as well as the pneumatic system discussed above, are fairly expensive and, thus, manufacturers of earthworking tools are constantly striving toward producing a better mechanism which is capable of being produced at a reduced cost without sacrificing any benefits gained from the unit during operation.